High molecular weight hydrocarbon soluble polymers, such as polyisobutylene, polystyrene, and several alpha olefins, have been demonstrated to reduce drag in turbulent flows of hydrocarbon liquids. Generally, the drag reduction effectiveness of these polymers improves with increasing molecular weight; however, the tendency for the polymers to permanently degrade via molecular scission in local extensional flows within pumps or turbulent pipeflows also increases with increasing polymer molecular weight. This invention discloses efficient drag reduction in hydrocarbon liquids resulting from a novel class of copolymers of an alpha olefin and a vinylalkylene carboxylic ester. The drag reduction agents of the instant invention are copolymers of an alpha olefin and a vinylalkylene carboxylic ester.
It is well known that alpha olefins can be polymerized in the presence of coordination catalysts (Ziegler Natta). These catalysts generally consist of materials such as transition metal halides (e.g., TiCl.sub.3) and organometallic co catalysts (e.g., R.sub.3 Al or R.sub.2 AlCl). Most of the efforts of this field have centered on maximizing catalyst activity and polymer stereoregularity/crystallinity (e.g., U.S. Pat. Nos. 3,116,274; 3,476,730; 3,156,681; 4,240,928). Items of commerce in this category are isotatic polypropylene and poly(1-butene). These stereoregular, crystalline polymers have excellent physical and mechanical properties and are well suited to forming molded objects such as pipe or tubing which require rigidity. However, these materials have limited use as polymer additives to hydrocarbon solutions (e.g., viscosifiers, drag reducers, antimist agents.)
A smaller body of knowledge exists on the preparation of ultra-high molecular weight noncrystalline alpha olefins, suitable for use as hydrocarbon viscosifiers, drag reducing agents, or antimist additives, etc. Examples of such art is found in U.S. Pat. Nos. 4,289,679; 4,358,572; 4,371,455 and British Pat. No. GR 2074,175A. The noncrystalline nature of these polymers make them amenable to easy dissolution in hydrocarbon media. However, these materials are completely nonfunctional and the solution properties of such can be optimized only be adjustment of polymer molecular weight (+distribution). In other words, there are no reactive groups on these chains suitable for modification or interaction.
Reports of functional alpha olefins in Ziegler Natta polymerizations are sparse. A notable exception is the copolymerization of propylene with the methyl ester of undecanoic acid (Japanese Patent Applications 57-152767, 57-188996, 57-188997). However, the product of this reaction is characterized by very low levels (0.1-0.3 mole % ) of functional group incorporation. Also, this polymer product is highly crystalline and thus not useful as hydrocarbon viscosifiers, drag reducing agents or antimist additives.
The instant invention is distinguished from the functional/short chain alpha olefin art (Japanese Patent Applications 57-152767, 57-188996, 57-188997) by the lower levels of crystallinity. Thus, the instant composition is useful for hydrocarbon solution applications; e.g., drag reduction, viscosification, antimisting additives etc., whereas the crystalline polymers of prior art are not. Moreover, it is surprising that although the instant invention and the art in Japan Patent Applications 57-152767, 57-188996 and 57-188997 differ only in length of R.sub.1, the instant invention achieves 2 to 5 times more functional group incorporation under similar process conditions.
U.S. Pat. No. 3,278,495 is directed to a terpolymer of ethylene, propylene and an unsaturated carboxylic acid and is clearly patentably and chemically distinct from the copolymers of the instant invention which are drag reduction agents.
U.S. Pat. No. 3,287,335 teaches a copolymer of an alpha olefin and a vinyl alkanoate or alkyl acrylate which are used for making films or textiles and are clearly patentably and chemically distinct from the polymers of the instant invention which are drag reduction agents.
The present invention discloses drag reduction agents for hydrocarbon liquids which are copolymers of an alpha olefin and a vinylalkylene carboxylic ester.